How to get world coordinates of a UV parameter on a NURBS Curve Surface?
This isn't supported, in general Blender's nurbs support is quite basic.

Blender uses a method of calculating nurbs that steps over the curve in U and V directions at a fixed level of subdivisions (tessellated for drawing in the viewport), and there are no built-in methods to ray-cast into a nurbs surface, though such methods exist and could be added to Blender.

However if you really wanted its possible to take the nurbs data (before tessellation) and evaluate it from Python, but this would be quite an involved task.

As a simple solution you could just get the mesh of a nurbs object and (knowing the order of grid verts/faces), you could find the face that lies on a UV coord, then interpolate across the face... it wont give an accurate location but may be good-enough in some cases.